Contractile properties of human nasal dilator motor units.
Contractile properties of human nasal dilator motor units.
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人鼻扩张器运动单位的收缩特性。
DOI：
10.1152/jn.1998.79.1.371
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
Fregosi,RF
中科院分区：
文献类型：
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作者：
Mateika,JH;Essif,EG;Dellorusso,C;Fregosi,RF
Mateika，J. H.，E. G. Essif，C. DelloRusso 和 R. F. Fregosi.人类鼻扩张器运动单位的收缩特性。 Neurophysiol.79: 371–378, 1998。肌内微刺激技术用于激活面部神经纤维，同时获取同步抽搐力测量值，以测量人类鼻扩张器 (ND) 运动单位的收缩特性和力频率响应。记录了 37 名受试者的 98 个 ND 运动单位的抽搐力幅度 (TF)、收缩时间 (CT)、半松弛时间 (HRT) 和归一化至峰值力的最大力上升率（最大收缩率，MCR）。平均CT、HRT、MCR和TF分别为47.9±1.8ms、42.6±2.1ms、28.6±1.8s−1和1.06±0.1mN。 CT 和 HRT 均与 TF 不显着相关。平均 CT 和 HRT 与手部小肌肉记录的值相似，但比人类脚趾伸肌运动单位记录的值更快。然而，抽搐力与 CT 或 HRT 之间缺乏关联，这与人类手部和足部肌肉的研究结果相似。记录八个 ND 运动单元的力-频率曲线。记录八个运动单位响应 1、5、10、15、20、25、30、35 和 40 Hz 的刺激而产生的力，以评估力-频率关系。八个运动单位的平均抽搐力为 0.91 ± 0.3 mN，平均强直力为 8.1 ± 1.8 mN。因此平均抽搐力等于强直力的12.7%。 50% 的单位强直力是在平均频率 16.4 ± 1.7 Hz 时实现的，该频率大于人类脚趾伸肌运动单位记录的值 (9.6 Hz)。因此，ND 运动单元产生的力对~10-30 Hz 范围内的放电频率变化更敏感，而由于其快速收缩特性，对 0-10 Hz 范围内的变化不太敏感。与每条力-频率曲线的陡峭部分拟合的回归线的平均斜率是力/Hz 的 5.15 ± 0.5% 变化。该值大于人类脚趾伸肌测量的斜率（力/Hz 变化 4.2%）。这些观察结果表明，ND 运动单位的力分级比人类脚趾伸肌运动单位对刺激频率的变化更敏感。我们得出的结论是，大多数 ND 运动单位具有快速收缩特性，并且速率编码可能在 ND 肌肉产生的力的分级中发挥重要作用。此外，这项调查的结果表明，人类面部肌肉的收缩速度和 TF 不相关。这支持了之前从人类手部和足部肌肉中获得的发现，并表明许多人类肌肉和其他哺乳动物的大多数肌肉之间的收缩速度-抽搐力关系可能存在根本差异。
Mateika, J. H., E. G. Essif, C. DelloRusso, and R. F. Fregosi.Contractile properties of human nasal dilator motor units.J. Neurophysiol.79: 371–378, 1998. The technique of intramuscular microstimulation was used to activate facial nerve fibers while acquiring simultaneous twitch force measurements to measure the contractile properties and force-frequency responses of human nasal dilator (ND) motor units. Twitch force amplitude (TF), contraction time (CT), half-relaxation time (HRT), and the maximal rate of rise of force normalized to the peak force (maximum contraction rate, MCR) were recorded from 98 ND motor units in 37 subjects. The average CT, HRT, MCR, and TF were 47.9 ± 1.8 ms, 42.6 ± 2.1 ms, 28.6 ± 1.8 s−1, and 1.06 ± 0.1 mN, respectively. Neither CT nor HRT were significantly correlated with TF. The average CT and HRT were similar to values recorded for small muscles of the hand but were faster than the values recorded from human toe extensor motor units. However the lack of an association between twitch force and CT or HRT was similar to the findings obtained for both human hand and foot muscles. Force-frequency curves were recorded from eight ND motor units. The force produced by the eight motor units was recorded in response to stimuli delivered at 1, 5, 10, 15, 20, 25, 30, 35, and 40 Hz to assess force-frequency relationships. The mean twitch force of the eight motor units was 0.91 ± 0.3 mN and the average tetanic force was 8.1 ± 1.8 mN. Therefore the average twitch force was equal to 12.7% of the tetanic force. Fifty percent of the unit tetanic force was achieved at an average frequency of 16.4 ± 1.7 Hz, which is greater than the value recorded for human toe extensor motor units (9.6 Hz). Thus the force produced by the ND motor units was more sensitive to changes in discharge frequency over the range of ∼10–30 Hz and less sensitive to changes in the range of 0–10 Hz because of their fast contractile properties. The mean slope of the regression lines that were fit to the steep portion of each force-frequency curve was 5.15 ± 0.5% change in force/Hz. This value was greater than the slope measured for human toe extensor muscles (4.2% change in force/Hz). These observations suggest that force gradation by ND motor units is more sensitive to changes in stimulation frequency than human toe extensor motor units. We conclude that most ND motor units have fast contractile properties and that rate coding may play a significant role in the gradation of force produced by the ND muscle. Furthermore, the findings of this investigation have demonstrated that contractile speed and TF in a human facial muscle are not correlated. This supports previous findings obtained from human hand and foot muscles and suggests that there may be a fundamental difference in the contractile speed-twitch force relationship between many human muscles and most muscles of other mammals.